News Scan for Mar 18, 2020

C diff testing intervention
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Carbapenem heteroresistance
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Lassa fever in Nigeria

Study suggests clinical support tool safely reduces C diff testing

A computerized clinical support tool implemented at an academic medical center helped reduce rates of Clostridioides difficile testing without an associated increase in adverse events in patients whose tests were prevented, researchers from the University of Virginia (UVA) School of Medicine reported today in Open Forum Infectious Diseases.

In the retrospective case control study, researchers examined the outcomes of patients admitted to the UVA Medical Center after the introduction of a computerized clinical decision support tool designed to reduce nucleic acid amplification tests (NAATs) for C difficile. NAAT tests are highly sensitive, but cannot distinguish between C difficile colonization and infection, and overdiagnosis of C difficile infection is thought to be linked to inappropriate testing in patients with low pre-test probability for infection.

A previous study had found a 41% reduction in C difficile testing at the hospital after introduction of the tool, and the researchers wanted to compare the safety of the intervention among patients with prevented tests and those with negative tests.

The multivariate analysis of 637 cases (490 negative, 147 prevented) showed that a prevented test was not significantly associated with the primary composite outcome of inpatient mortality or intensive care unit transfer compared with a negative test (adjusted odds ratio, 0.912, P = .747), and that patients in the prevented group had shorter lengths of hospital stay (median 6 days, compared with 9 in the negative-test group). Of the 147 patients with a prevented test, 54 (37%) went on to have a completed test within 7 days, and 11 were positive, resulting in a potential delay in diagnosis. But individual case reviews found that either clinical changes warranted the delay in testing or no adverse events occurred that were attributable to C difficile infection—a finding that suggests the tool isn't discouraging appropriate testing.

"Diagnostic stewardship of C. difficile testing using computerized clinical decision support may be both safe and effective for reducing inappropriate testing," the authors of the study concluded.
Mar 18 Open Forum Infect Dis abstract

 

Study highlights prevalence of heteroresistance in ESBL isolates

A new study by researchers at the University of Southern California School of Pharmacy has found that nearly a third of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae isolates from patients were identified as being heteroresistant to carbapenems. The findings were published yesterday in the Journal of Antimicrobial Chemotherapy.

In the study, 173 ESBL-producing Escherichia coli and Klebsiella pneumoniae isolates from patients with recurrent infections that were reported as meropenem susceptible were tested for heteroresistance—a condition in which different bacterial populations from the same isolate exhibit varying susceptibilities to the same agent. Heteroresistance was screened by disc diffusion and confirmed by a modified population analysis profiling (PAP) method against ertapenem, imipenem, meropenem, and ceftolozane/tazobactam.

A total of 519 bacteria/carbapenem combinations were screened by disc diffusion, with 84 combinations identified as carbapenem heteroresistant (cHR). Modified PAP confirmed 70 bacteria/carbapenem combinations as cHR, with the heteroresistant phenotype most frequently observed against ertapenem. In total, 32% of the unique patient isolates (55/173) were identified as being heteroresistant to at least one carbapenem, and 16% of those patients (9/55) had a carbapenem non-susceptible isolate on a subsequent visit. More cHR isolates originated from a non-urinary source compared with non-cHR isolates (31% vs 19%, P = 0.02).

The authors of the study say the findings raise "significant concerns" about the continued use of carbapenems as first-line therapy for serious ESBL-producing E coli and K pneumoniae infections, and say more research is needed into the contribution of antibiotic exposure to the development of cHR phenotypes.
Mar 17 J Antimicrob Chemother abstract

 

Lassa fever cases reach record levels in Nigeria

Nigeria is experiencing its largest Lassa fever outbreak, and the Nigerian Academy of Science (NAS) is pushing for the government to declare a national health emergency, Devex, a media platform of the global development community, reported today.

The outbreak of the viral hemorrhagic fever has been linked to 161 deaths so far this year. Nigeria typically has annual outbreaks during the dry season, which runs from November to May, but cases have increased from year to year in recent years. So far this year, health officials have reported 3,735 cases, with 906 lab confirmed. For comparison, there were 810 confirmed cases in 2019, 633 in 2018, and 308 in 2017.

NAS experts said increased populations of the rodents that spread the virus could be fueling the increases, and some have suggested a role for climate change. The disease is caused by indirect exposure to or direct contact with infected Mastomys rats.
Mar 18 Devex story

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